Balloon structure with PTFE component

ABSTRACT

A medical balloon having a high burst strength and the ability to return to its preinflation diameter following repeated inflation may be prepared from a first inner layer of material, a second intermediate layer of expanded PTFE and a third outer layer of material.

FIELD OF THE INVENTION

The present invention relates generally to medical balloons made atleast in part from polytetrafluoroethylene.

BACKGROUND OF THE INVENTION

The use of medical balloons for dilatation of a body vessel as well asfor expansion and seating of a medical devices such as a stent is wellknown. Medical balloon may be made of a single layer of material or ofmultiple layers of material. In the case of multilayer balloons, themultiple layers may be of the same or different materials.

A variety of materials have been used for making medical balloonsincluding thermoplastic polyurethanes (TPU), polyethylene, polyesterssuch as polyethylene terephthalate (PET) including non-compliant PET,Arnitel, Hytrel, polyetherether ketone (PEEK), block copolymers ofpolyether polymers and polyamides (polyether block amides) such asPebax® (all grades) available from Elf Atochem North America, blockcopolymers of polyether and polyester polymers such as Hytrel® availablefrom E. I. DuPont de Nemours & Co. in Wilmington, Del., Teflon®,polyamides such as nylon-11 and nylon-12, block polyimides,polytetrafluoroethylene (PTFE), polyolefins such as polyethylenes (PE)and polypropylenes (PP), synthetic rubbers including SBR and EPDM, aswell as other polyolefins and silicone elastomers. For catheter balloonsused in coronary angioplasty preferred polymeric substrates are PET,nylon and PE. The specific choice of materials depends on the desiredcharacteristics of the balloon.

Of these materials, PTFE is of interest for use in medical balloonsbecause of its low coefficient of friction, chemical resistance,flexibility and strength. Because of the physical properties of PTFE,however, the material cannot be processed in the same way thatconventional thermoplastic elastomers are processed.

The use of polytetrafluoroethylene (PTFE) and expanded PTFE (EPTFE) inimplantable medical devices such as balloons has been disclosed in U.S.Pat. No. 5,752,934 and U.S. Pat. No. 5,868,704 both of which disclose aballoon comprised of a porous EPTFE layer and an elastomeric orinelastic layer. The EPTFE films may serve either as a coat for aballoon or as an integral part of a balloon in the form of an outerlayer. The balloons disclosed therein are formed from a helically woundporous EPTFE film. In one example, twenty layers of EPTFE film are usedto form the EPTFE portion of the balloon. As a result, these balloonstend to have a large profile.

It is desirable to produce a medical balloon which has some of theproperties of a PTFE balloon and yet has a low profile. Morespecifically, it is a goal of the present invention to provide anon-compliant EPTFE balloon which has a high burst strength and theability to return to its preinflation diameter following repeatedinflation/deflation cycles. To that end, the present invention providesmedical balloons having one or more EPTFE layers disposed between aninner balloon material and an outer balloon material.

All US patents and all other published documents mentioned anywhere inthis application are incorporated herein by reference in their entirety.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to medical balloons comprising EPTFEand similar materials as well as to catheters with such balloons mountedthereon. At least a portion of the medical balloon disclosed hereinincludes an inner layer, an intermediate layer and an outer layer. Theintermediate layer disposed between the inner and outer layers is formedof EPTFE. A wide variety of materials may be used for the inner andouter layers including thermoplastic materials, elastomeric materialsand thermoplastic elastomeric materials.

The intermediate expanded PTFE layer may extend over the entire lengthof the balloon or may extend over only a portion of the balloon.

The present invention is also directed to a balloon having a first bodyportion with a generally linear compliance curve to burst pressure and asecond body portion having a stepped compliance curve.

The balloons of the present invention may be formed in a variety of waysincluding coating the interior and exterior of an EPTFE tube with firstand second materials or laminating an inner and an outer layer ofmaterial to one or more layers of EPTFE at a suitable temperature.Alternatively, the balloon may be formed by inserting a PTFE or an EPTFEtube between inner and outer tubes of other materials and suitablyshaping the tubes at a desired temperature via the application oftension and/or radially outward pressure such as by blowing. Where aPTFE tube is used, the PTFE may be expanded during the step of radiallyexpanding the tube so as to form an EPTFE tube. The EPTFE tube may alsobe formed by expanding an extruded tube of PTFE separate from radialexpansion or may be formed of a sheet of EPTFE that is disposed in atubular form.

The present invention is also directed to methods of preparing theinventive balloon. One such method involves coating a tube of PTFE orEPTFE on the inside and outside. Another method involves concentricallydisposing inner, outer and intermediate tubes and joining the tubestogether via lamination or heating or any other suitable technique. Yetanother method involves co-extruding the three or more layers of balloonmaterial.

The inventive catheters include the medical balloon disclosed hereindisposed about a tube and having an inflation lumen in fluidcommunication with the balloon. The inventive catheter may be dilatationcatheters, a medical device delivery catheter or any other catheter thatcarries a medical balloon.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1a shows a node and fibril structure for EPTFE have substantiallyparallel fibrils.

FIG. 1b shows a node and fibril structure for EPTFE in which the fibrilsare bent.

FIG. 2 shows a longitudinal cross section view of a medical balloon withan intermediate layer extending only over the body portion of theballoon.

FIG. 3 shows a longitudinal cross section view of a medical balloon withan intermediate layer extending over the cone portion of the balloon.

FIG. 4 shows a longitudinal cross section view of a medical balloon withan intermediate layer extending over a part of the waist portion of theballoon.

FIG. 5 shows a longitudinal cross section view of a medical balloon withan intermediate layer extending over the waist portion of the balloon.

FIG. 6 shows a longitudinal cross section view of a medical balloon withan encapsulated intermediate layer.

FIG. 7a shows a schematic view of a fully inflated balloon.

FIG. 7b shows a schematic view of a partially inflated balloon.

FIG. 7c shows a longitudinal cross section of the balloon of FIG. 7balong lines 8—8.

FIG. 8 shows a balloon mounted on a catheter.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein specific preferred embodiments of theinvention. This description is an exemplification of the principles ofthe invention and is not intended to limit the invention to theparticular embodiments illustrated.

The inventive medical balloons disclosed herein may be used for avariety of purposes including angioplasty and embolectomy as well as forthe expansion of medical devices such as stents, grafts, stent-graftsand vena-cava filters.

The inventive medical balloons are generally characterized by thepresence of at least one intermediate layer of a fluorinated polymericmaterial such as PTFE, or EPTFE or materials such as a linear highdensity polyethylene disposed between an inner layer of a first balloonmaterial different from the material of the intermediate layer and anouter layer of a second balloon material different from the material ofthe intermediate layer. The first and second balloon materials may bethe same or different from each other.

A suitable form of PTFE may be made in accordance with U.S. Pat. No.5,480,711. An example of a PTFE material is manufactured by DuPont deNemours & Co. in Wilmington, Del. under the tradename of Teflon®.Suitable EPTFE films may be made in accordance with U.S. Pat. No.3,953,566 and 4,187,390. This form of EPTFE, shown in FIG. 1a, has amicrostructure consisting of nodes 102 interconnected by fibrils 104which are all substantially parallel to the direction of expansion. Moredesirably, the EPTFE used in the inventive balloons disclosed hereinwill have a microstructure as shown in FIG. 1b consisting of nodes 102interconnected by bent or wavy fibrils 104. This latter form of EPTFE,disclosed in U.S. Pat. No. 5,752,934, is more elastic than the EPTFEdisclosed in either U.S. Pat. No. 3,953,566 or U.S. Pat. No. 4,187,390and is characterized by a rapid recovery of greater than 5.5%. Allpatents referred to are herein incorporated in their entirety.

In one embodiment, as shown in FIG. 2, inventive balloon 112 is formedof three layers including an inner layer 118, an intermediate layer 122formed of expanded PTFE and an outer layer 126. In the embodiment shownin FIG. 1, intermediate layer 122 extends over body portion 130 ofballoon 110.

In another embodiment, shown in FIG. 3, intermediate layer 122 extendsbeyond the body portion to at least a portion of the proximal and distalcone 134 portions.

In another embodiment, shown in FIG. 4, intermediate layer 122 extendsover at least a portion of proximal and distal waist 138 portions.

In another embodiment, shown in FIG. 5, intermediate layer 122 iscoextensive with inner layer 118 and outer layer 126 over the length ofballoon 110.

The invention is also directed to a medical balloon, shown at 112 inFIG. 6, containing at least an inner layer 118, an outer layer 126 andan intermediate layer 122. Intermediate layer 122 is enclosed orencapsulated by inner layer 118 and outer layer 126. Inner layer 118 andouter layer 126 are joined together so as to encapsulate intermediatelayer 122. As shown in FIG. 6, inner layer 118 and outer layer 126 arejoined at proximal and distal waists 138. They may also be joined incone portions 134.

In yet another embodiment, the invention is directed to a medicalballoon containing, as above, an innermost layer, an outer most layerdisposed exterior to the innermost layer, and an intermediate layer,disposed between the innermost layer and the outermost layer. Theintermediate layer is constructed of a material having a node structureconnected by multiple fibers. Suitable materials having such a structureinclude expanded PTFE and high density polyethylene. Desirably, thefibers will be bent or wavy.

In yet another embodiment, the invention is directed to a medicalballoon having, as above, an innermost layer, an outer most layerdisposed exterior to the innermost layer, and an intermediate layer,disposed between the innermost layer and the outermost layer. Theintermediate layer is constructed of a material which, when expanded,has a node structure connected by multiple fibers.

The above-described inventive balloons may be prepared, via the choiceof suitable inner and outer materials, so as to display normaldistention at low inflation pressures and reduced distention at highpressures.

In another embodiment, the invention is directed to a balloon, shown at112 in FIG. 7a, having first and second adjacent body longitudinalportions, labeled 130 a and 130 b respectively. First body portion 130 ahas a generally linear compliance curve to burst pressure. Second bodyportion 130 b has a stepped compliance curve characterized by a lowpressure segment generally collinear with the corresponding segment ofthe first body portion, a transition segment during which the balloonexpands rapidly relative to the first body portion and a high pressuresegment during which the compliance curve of the second portion expandsslowly relative to the transition region. Balloon 112 is shown in thepartially inflated state in FIG. 7b at a pressure where the compliancecurves of the first and second body portions are generally collinear. Across-sectional view of balloon 112 is shown in FIG. 7c. Inner layer 118and outer layer 126 extend over the length of the balloon. Anintermediate layer 122 extends along the length of body portion 130 a onboth sides of the balloon and is discontinuous in the region of secondbody portion 130 b. The discontinuity is shown at 132.

In the embodiment of FIGS. 7a-c, the inner and outer materials arecharacterized by a compliance curve similar to that of the secondportion of the balloon while the intermediate layer is characterized bya compliance curve similar to that of the first portion of the balloon.

Desirably, the intermediate layer will be formed of a fluoropolymer suchas PTFE or the expanded PTFE's discussed above, or of a high densitypolyethylene.

Balloons whose sections are characterized by different compliance curvesare discussed more generally in U.S. Pat. No. 574,985, U.S. Pat. No.5,447,497 and U.S. Pat. No. 5,358,487 incorporated by reference hereinin their entirety.

The instant invention is also directed to methods of forming aninventive balloon preform as well as a balloon. In one such method, atube made of EPTFE is provided. The EPTFE tube may be formed of anextruded PTFE tube which has been stretched under suitable conditions orstretched and compressed under suitable conditions. A suitable extrudedEPTFE tube may be made in accordance with U.S. Pat. No. 5,505,887incorporated by reference herein in its entirety. The EPTFE tube mayalso be formed by disposing a sheet of EPTFE (desirably withsubstantially parallel or bent fibrils) in a tubular form and sealingthe two adjacent edges by heating the tube at a suitable temperature.This sheet may be formed of one layer of EPTFE, or of a multitude oflayers of EPTFE including two or more. The layers may be heated forformation of a seal between said layers.

The inside of the tube is coated with a first material and the outsideof the tube is coated with a second material. Where the same material isused for the inside and outside of the tube, the coating may beaccomplished by immersing the tube in a bath of the coating material orthrough other suitably coating techniques including spraying thecoating, painting the coating onto the tube or extruding the materialonto the interior and exterior of the tube. Where different materialsare used for the inner and outer layers, the coating may be applied byspraying the tube, painting the material on the tube, extruding thematerials or any other suitable application process. Immersiontechniques may also be employed if the portion not being coated isappropriately masked.

The resulting tube may either be used directly as a balloon or, moredesirably, as a balloon preform for additional processing so as to forma balloon therefrom. In the latter case, the preform may be shaped at apredetermined temperature through suitable balloon forming techniques,as are known in the art. The shaping process may include the applicationof tension to the balloon so as to stretch it and/or the application ofa uniform radial outward force by blowing the preform.

Desirably, the preform will be subject to a temperature ranging fromabout 70° to about 100° C. and subject to a tension of about 20 g toabout 200 g, followed by blowing at pressure of about 200 psi to about600 psi. Of course, other suitable operational parameters may be used aswell. The formation of balloons from preforms is well known in the artand is described for instance in U.S. Pat. No. 4,490,421, in U.S. Pat.No. 5,807,520, and U.S. Pat. No. 5,348,538, all herein incorporated byreference in their entirety.

A balloon with an EPTFE layer may also be prepared by radially expandinga tubular preform containing a PTFE layer.

The invention also contemplates a method of forming an inventive ballooncomprising the steps of providing first, second and third tubes,inserting the first tube into the second tube, inserting the second tubeinto the third tube, inserting the first second and third tubes into aballoon mold and expanding the first, second and third tubes at adesired temperature so as to form a balloon. The second tube is formedof EPTFE.

Another method for forming the inventive balloon comprises the steps ofcoextruding first, second and third materials so as to form a balloonpreform. The second material is a fluoropolymer such as PTFE or a highdensity polyethylene and is disposed between the first and secondmaterials. Where an EPTFE tube is desired, the balloon preform may bestretched and treated so as to form EPTFE. The resulting balloon preformmay be shaped to form a balloon. The shaping may be carried out at adesired temperature and by the placing the preform in tension, byblowing the preform or by a combination of placing the balloon undertension and blowing the balloon or through any other suitable techniqueknown in the art.

The inventive balloons may also be formed by providing a first tube of afirst material and disposing a sheet of PTFE, EPTFE, high densitypolyethylene or other suitable material as disclosed herein around thefirst tube. A second material may then be disposed around the first tubeor the first tube may be placed within a second tube of a secondmaterial which serves as the outer skin of the balloon. The materialsare then heated to laminate them together or to laminate the material ofthe first tube to the outer second material. The materials may also beadhesively joined together using suitable adhesives as are known in theart.

It is noted that in the case where an intermediate layer of PTFE is usedin a balloon preform, the PTFE may be expanded on blowing the preform sothat the PTFE layer in the preform is transformed to an EPTFE layer inthe finished balloon.

It is also noted that on blowing the laminated balloon preforms, theintermediate layer such as PTFE, EPTFE, polyethylene or the like maydelaminate from the inner and outer layers thereby encapsulating theintermediate layer.

In another embodiment, the invention is also directed to a catheterhaving a medical balloon disposed thereon. FIG. 8 shows a balloon 212disposed about a catheter tube 210. Guidewire 213 runs through cathetertube 210. Catheter tube 210 is in fluid communication with balloon 212.Alternatively, a separate inflation lumen (not shown) may be providedfor inflating the balloon. As further shown in FIG. 8, catheter 210 isin vessel 214 having a lesion 216 therein. Balloon 212 is located inlesion 216 and is shown in a partially inflated state right beforedilatation of the vessel.

The inventive balloons disclosed herein are not limited to three layerballoons. More generally, the inventive balloons may be formed of threeor more layers of material with at least one intermediate layer ofmaterial being of a material selected from the group consisting offluoropolymers and high density polyethylene as discussed above.

The invention is also directed to other types of catheters includingmedical device delivery catheters which can employ the inventiveballoons. One such suitable stent delivery catheter is disclosed in U.S.Pat. No. 5,772,669 to Vrba. The inventive catheters may be ofover-the-wire design, fixed-wire design, rapid exchange design or anyother suitable design as is known in the art.

The above disclosure is intended to be illustrative of the presentinveniton, and is not exclusive. This description will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be encompassed withinthe scope of the attached claims. Those familiar with the art mayrecognize other equivalents to the specific embodiments described hereinwhich equivalents are also intended to be encompassed by the claimsattached hereto.

EXAMPLES Example 1

The outer and inner layers of a structure balloon was made from tubularpreforms which were made of Arnitel® EM-740. A middle layer was formedfrom ePTFE. The two Arnitel® EM-740 tubes had inside and outsidediameters of 0.043 cm (0.017 inches) and 0.079 cm (0.031 inches)respectively for the inner tube and 0.127 cm (0.050 inches) and 0.152 cm(0.060 inches) respectively for the outside tube. The tubes were thenassembled together coaxially resulting in a sandwich structure and theassembly was subjected to stretching at room temperature withoutelongating the ePTFE tube.

The sandwich structure was then inserted into a mold and formed into a3.0 mm balloon at 95 degrees celcius with a blow pressure of 450 psi (31atm) and tension of 70 grams. The resultant three-layer balloon had awall thickness of 0.00643 cm (0.00253 inches), a compliance of 5.1% at6-12 atm and 5.5% at 12-18 atm and burst pressure was 353 psi (24 atm).

The resultant balloon had a much higher puncture resistance than asingle layer balloon made from Arnitel® EM-740 only with the same wallthickness.

The resultant balloon had a sandwich structure.

What is claimed is:
 1. A medical balloon having a proximal waistportion, a proximal cone portion, a body portion, a distal cone portionand a distal waist portion, said medical balloon further having at leasta portion of which has at least three layers including i) an inner layerwhich defines the balloon structure made of a first material; ii) anouter layer coextensive with the inner layer made of a second material;and iii) an intermediate layer extending only over the body portion andbetween the inner lair and the outer layer which is formed of a materialhaving a node and fibril structure; wherein the intermediate layer isdisposed between the inner and outer layers and the first and secondmaterials differ from the material of the intermediate layer, which isselected from the group consist of expanded polytetrafluoroethylene andhigh density polyethylene.
 2. A medical balloon in laminated form atleast a portion of which has at least three layers including i) an innerlayer which defines the balloon structure made of a first material; ii)an outer raver coextensive with the inner layer made of a secondmaterial; and iii) an intermediate layer between the inner layer and theouter layer which is formed of a material having a node and fibrilstructure, which is selected from the group consisting of expandedpolytetrafluoroethylene and high density polyethylene; wherein theintermediate layer is disposed between the inner and outer layers andthe first and second material differ from the material of theintermediate layer and the inner layer is laminated to the intermediatelayer and the intermediate layer is laminated to the outer layer.
 3. Amedical balloon at least a portion of which has at least three layersincluding i) an inner layer which defines the balloon structure made ofa first material; ii) an outer layer coextensive with the inner layermade of a second material; and iii) an intermediate layer between theinner layer and the outer layer which is formed of a material having anode and fibril structure, which is selected from the group consistingof expanded polytetrafluoroethylene and high density polyethylene;wherein the intermediate layer is disposed between the inner and outerlayers and the first and second materials differ from the material ofthe intermediate layer and the intermediate layer extends over only aportion of the medical balloon.
 4. A medical balloon at least a portionof which has at least three layers including: i) an inner layer whichdefines the balloon structure made of a first material; ii) an outerlayer coextensive with the inner layer made of a second material; andiii) an intermediate layer between the inner layer and the outer layerwhich is formed of a material having a node and fibril structureselected from the group consisting of expanded polytetrafluoroethyleneand high density polyethylene; wherein the intermediate layer isdisposed between the inner layer and outer layers and is encapsulatedbetween the inner and the outer layer and the inner layer is laminatedto the intermediate layer and the intermediate layer is laminated to theouter layer.